The present disclosure relates generally to gas turbine engine exhaust cases. More particularly, the present disclosure relates to sealing arrangements between the exhaust case and other structural components of the gas turbine engine.
Turbine Exhaust Cases (TEC) typically comprise structural frames that support the very aft end of a gas turbine engine. In aircraft applications, the TEC can be utilized to mount the engine to the aircraft airframe. In industrial gas turbine applications, the TEC can be utilized to couple the gas turbine engine to an electrical generator. A typical TEC comprises an outer ring that couples to the outer diameter case of the low pressure turbine, an inner ring that surrounds the engine centerline so as to support shafting in the engine, and a plurality of struts connecting the inner and outer rings. As such, the TEC is typically subject to various types of loading, thereby requiring the TEC to be structurally strong and rigid. Due to the placement of the TEC within the hot gas stream exhausted from a combustor of the gas turbine engine, it is typically desirable to shield the TEC structural frame with a fairing that is able to withstand direct impingement of the hot gases. The fairing additionally takes on a ring-strut-ring configuration wherein the struts are hollow to surround the frame struts. The structural frame and the fairing can each be made of materials optimized for their respective functions.
When mounting the TEC to other structural components of a gas turbine engine, such as a casing for a power turbine of an electrical generator, it is necessary to seal the gas path. Seals are used to prevent leakage of exhaust gas from the gas path, which reduces efficiency of the power turbine, and to prevent cooling air from entering the gas path, which reduces efficiency of the gas turbine engine. It is therefore desirable to seal, for example, between the fairing and the TEC, as well as between the TEC and the power turbine. However, due to the specific geometries of these various components, it is sometimes necessary to seal across lengthy distances. Finger seals are typically used in such circumstances. In general, a finger seal becomes more inefficient as the gap over which it seals grows. Furthermore, the finger seal can become fatigued if it repeatedly deflects over a long distance. There is, therefore, a need for improved sealing arrangements between structural components in gas turbine engines.